Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

745
FXUS63 KLOT 051202
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
702 AM CDT Sun Jul 5 2026

.KEY MESSAGES...

- Isolated to widely scattered showers are expected this morning
  near Lake Michigan.

- Scattered showers and thunderstorms (20-40% chance) are
  expected this afternoon mainly near/south of I-80, but many
  areas will remain dry.

- Drier and more seasonable conditions are expected to start
  the week before stormier weather returns late week.

&&

.DISCUSSION...
Issued at 253 AM CDT Sun Jul 5 2026

A baggy shortwave trough continues to reside over the western
Great Lakes early this morning. Beneath the trough very
saturated low-levels are keeping low stratus and fog across
much of northern IL and northwest IN, with the worst of the fog
over the Chicago metro and near Lake Michigan (basically areas
that saw the heaviest rainfall yesterday). This fog is expected
to linger through daybreak before eroding, but the threat for
widespread dense fog appears to be waning.

The main forecast item of concern early this morning is whether
or not more robust showers and perhaps an isolated storm will
develop over the next several hours within the spotty showers
already ongoing early this morning near Lake Michigan. While
there is certainly enough moisture, the question is whether the
forcing associated with the trough overhead and the broad
surface low over southern Lake Michigan will be sufficient for
more robust showers to develop. The main concern would be a
threat for locally heavy rainfall due to the high moisture
content and slow shower/storm motions which would lead to
renewed flooding should these set up over the Chicago metro or
anywhere that received heavy rain the past few days. With
guidance not really handling the ongoing showers across the
region, forecast confidence remains low. That said, have added
some 20-30% POPs to the forecast near Lake Michigan through the
morning to account for this potential and will continue to keep
a close eye on radar trends.

Any showers (and/or storms) that develop early this morning
will play a role on how things evolve this afternoon. If more
widespread showers occur then the coverage of scattered showers
and thunderstorms will likely be low and farther south.
However, if the morning coverage is lower (which is the favored
scenario) then a greater shower and thunderstorm coverage may
materialize. With a lot of uncertainty on how this morning will
play out, confidence on the coverage of afternoon showers/storms
is also low. That said, with the aforementioned surface low
expected to be traversing across lower MI later today, it seems
the better environment for storms this afternoon will be near
and south of the Kankakee River Valley (30-40% chance). As a
precaution have included some 20-25% POPs as far north as I-80
in case things develop farther north but suspect most areas
north of the Kankakee Valley should stay dry. Regardless of
storm coverage, the limited wind shear and much weaker
instability today should keep the severe threat virtually zero
but a heavy rain threat will still exist with localized gusty
winds up to 40 mph.

Otherwise, expect partly to mostly cloudy skies today with much
cooler temperatures compared to the past few days. Highs today
are only expected to top out in the lower 80s inland with those
near the lake only expected to be in the mid to upper 70s due to
the onshore winds. With winds expected to become a bit breezier
this afternoon (speeds around 10-15 mph with gusts up to 20
mph) waves on the lake should increase into the 2 to 4 feet
range this afternoon and evening. Though if winds verify a bit
higher then some locally higher waves up to 5 feet could be
seen. Bottom line, if you are heading to the beach today keep an
eye on the waves and if they become too high for your comfort
level then stay out of the water.

Heading into Monday, the trough overhead will be pivoting
eastward and pushing the shower and storm chances east and south
of our area. Temperatures on Monday will be on the seasonable
side with highs in the lower to mid-80s inland with 70s expected
near the lake due to persistent onshore winds. The dry weather
will prevail into Tuesday, but with winds expected to be more
southerly, temperatures should be a few degrees warmer with
highs in the mid to upper 80s. However, the potential for a lake
breeze Tuesday afternoon means that temperatures near the
immediate lake shore will likely be a tad cooler in the upper
70s to lower 80s.

The upper level pattern is still forecast to become more west-
southwesterly by Wednesday which will begin to advect in more
humid air back into the region, though temperatures do look to
stay more on the seasonable side with highs generally in the mid
to upper 80s. With the increasing humidity will bring increasing
chances for showers and thunderstorms for the latter half of
the week and into next weekend. While confidence is decently
high on the transition to another stormy pattern, the coverage
and intensity of storms each day remains uncertain so be sure to
check back for updates as we get closer.

Yack

&&

.AVIATION /12Z TAFS THROUGH 18Z MONDAY/...
Issued at 700 AM CDT Sun Jul 5 2026

Key aviation forecast messages:

- Low confidence in SHRA/TS trends through midday.

- A period of IFR CIGs may redevelop mid morning into early
  afternoon near Lake Michigan.

Shower coverage has decreased markedly over the past hour over
Cook County which may lead to a brief break in showers before
renewed development potentially occurs later this morning. Have
maintained a VCSH mention through the morning though. The
threat of TS continues to be rather low, but still can`t rule
out some lightning in any more robust isolated showers that
develop. Accounted for this in a PROB30 from 15-18Z at ORD/MDW,
though it is possible this ends up occurring south of the
terminals and I-80.

We are monitoring an area of IFR stratus currently in southeast
WI and far northeast IL that may try to pivot back south across
the metro later this morning. Lowered CIGs in the PROB30 groups
to BKN010 to account for this though it is possible IFR will
need to be introduced based on observational trends through the
morning. Generally expect CIGs to gradually improve during the
afternoon through sunset.

Light N to NNW winds will return to a prevailing northeast
direction by mid morning increasing to around 10-15 kt with a
few gusts to 20 kt possible through the day. Winds then ease
tonight, potentially returning to a NNW direction at times
before returning to NE and increasing back to around 10 kt on
Monday.

Petr

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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